Shaping tubular shells and ammunition cartridges



Jan. 16, 1968 A. J. DUFFIELD 3,363,296

SHAPING TUBULAR SHELLS AND AMMUNITION CARTRIDGES Filed April 15, 1964 F! WE T. l 1 l T I l l )0 I ,1 "H I? 1e 12 I! l H 1: l I? II PHA V w 24 l 'l J 12 l 12 I l8 8 FIG I 2 INVENTOR.

ALBERT J. DUFF/[L0 A TTORNEY United States Patent Ofi Fice 3,363,296 Patented Jan. l6, 1968 3 363,296 SHAPING TUBULAR SHELLS AND AMMUNITION CARTRIDGES Albert J. Duiiield, Woodbridge, Conn., assignor to Olin Mathieson Chemical Corporation, a corporation of Virginia Filed Apr. 15, 1964, Ser. No. 359,835 3 Claims. (Cl. 29--1.3)

This invention relates to making tubular containers such as cartridge cases and more particularly cartridge cases of improved mouth structure. By this invention, especially metal shotgun shells and blank shells are adapted to be crimped shut at the mouth in an improved way.

Heretofore such shells have been made from some material such as metal by a process of impact extrusion to produce a generally straight sidewall, the head flange and the primary pocket in one operation. By extrusion according to US Patent No. 2,088,525, for example, it has been possible to make shells of greater thickness at the head but not with a desirable thinning of the mouth. Attempts made at thinning the mouth by either reverse or forward extrusion has been accompanied by various disadvantages such as undesired wrinkling or other distortion and/ or crookedness in the sidewall.

In accordance wtih this invention, a cartridge is produced from a blank or slug of any suitable material, preferably aluminum, by extrusion of the blank done in such a way as to produce a predetermined length of cylindrical sidewall, which is integral with the cartridge base at one end and is integral with an extension at the opposite open end, and to further work the extruding material at that end by a limited circumferential stretching operation in the extension, all of which is followed by a mouth-thinning draw reforming the extension to have the same diameter as the adjacent sidewall. At this stage the material in the extension provides a highly worked mouth structure of rather abruptly reduced thickness starting from a desired taper. With metal this structure is further adapted for highly localized mouth annealing, which ia desirable where pie-cut or star-shaped crimping the shell mouth is done to make an integral folded shell closure, such as that shown in U.S. Patent No. 2,591,286, for example, but of an improved character, thereby avoiding the use of a top wad.

Another feature of the invention is the accomplishment of this objective using special working aparatus involving impact extrusion in a die up an orifice-forming and shell-supporting punch, one enlarged end of which is adapted to coact with the die to form an annular extrusion orifice and which is axially separated by exactly the desired length of sidewall from the other end of the punch which has a still greater enlargement adapted to produce the desired extension first by a bulging operation performed over the enlargement followed by a draw done in conjunction with the enlargement and the same die.

For the purpose of preferably forming an integral cartridge case rim at the base or head of the shell, the die has an annular constriction at the end on the same side as the punch.

The various objects and advantages of this invention will become evident from the following description of a preferred embodiment made in greater detail with reference to the accompanying drawing in which:

FIG. 1 is an elevational view partly in cross section showing a cylindrical slug or disc-like blank in position in die apparatus ready for producing a case and also showing in broken lines the cylindrical sidewall and end extension produced when the blank is operated upon in the first stage;

FIG. 2 is an elevational view partly in cross section showing a further stage in manufacture wherein the end extension is being subjected to a draw to accomplish thinning at the mouth and sizing to desired external diameter; and

FIG. 3 is a side view in cross section showing a typical finished shotgun cartridge made in accordance with this invention, thereby improving on US. Patent No. 2,582,- 124 by combining a flanged wad with a thinned closure.

To make a rimmed shotshell, a slug 1 is placed in the bore 11 of a forming die 12 having at one end a constriction 13 in comparison with which the bore 11 is an enlargement separated from the constriction by a cartridge rim-forming shoulder 14. Punch 16 is provided so that its end 17 in the position shown in FIG. 1 operates as a die mandrel in constriction 13. Into the other end of the die opposite the constriction and punch, a ram 18 is driven against the slug compressing it in the die, the ram, and the punch to extrude part of it as a cartridge sidewall portion 2 terminating in an extension 3 which is forced by the extrusion action to ride up the punch taper 20 to be subjected to a stretching and an increase in diameter over the punch enlargement 21. Punch end 17 and its enlargement 21 are separated by an intermediate portion 22 of diameter slightly less than that of end 17 so as to minimize friction which is a serious limitation to forming thin extruded sections of certain materials, even with metals.

For the first stage of operation, taper 20 and enlargement 21 are axially spaced from end 17 by a length exactly that of the finished tubular sidewall desired. Enlargement 2.1 is of larger diameter than end 17 but of less diameter than die constriction 13 for the purpose of the next stage, which is a draw. Here, for aluminum up to about a 40% reduction in mouth thickness was attained.

Punch end 17 has a recess 23 and is otherwise suitably configured to provide the desired internal base structure in the cartridge, the external structure of which is formed at the rear by the shape of the end face of ram 18 and any suitable central protrusion 24, locating the primer pocket.

The punch is mounted with clearance in a bore 26 of a die-supporting frame 27, so that there is room to clear the extension 3 formed. In the next stage of operation, the punch may be driven down in the die as the ram is retracted until both the bulged cartridge extension 3 and the punch enlargement 21 are driven sufficiently through die constriction 13, as shown in FIGURE 2 to provide thinning at the mouth 6, being formed from extension 3, and an external diameter there the same as that of portion 2. The latter remains as it was, attached at bevel 7 to mouth 6 and attached to base 8. The integral rim 9 formed in the first stage is grasped by a stripper to pull the case off the punch.

The material in the mouth is not only thinner than in the sidewall portion but is also more severely worked. With some material, this provides a desired increasing strength suitable for certain types of cartridge cases. Where further shaping and malleability is desired in the mouth, as in the shotshell for the purpose of crimping it shut to provide a yieldable and reusable closure, advantage may be taken of the thinness and accompanying improved physical properties obtainable at the mouth 6 as a result.

In a metal cartridge case, the resulting structure is especially suitable for subsequent mouth annealing because the abrupt change in section and localized intense working predispose the metal to recrystallize here at a lower and more sharply defined temperature. Consequently, heating need not be so sharply confined at the mouth as heretofore, since the abrupt difference in internal structure and thickness tends to prevent spread of the annealing into the sidewall portion 2.

FIGURE 3 shows a shotgun case made according to this invention to have the closed head 31 (finished from base 8 for receiving the primer 32 operably) a sidewall 33, equal to portion 2, for containing propellant charge 34, wad 35, and the shot 36, and end extension at shell mouth closure 37.

The extended mouth being thinner and joined at 38 by a somewhat abrupt change of section to the sidewall, is adapted to be pie-cut 0r star-shaped crimped and then folded inwardly to form the yieldable end closure 37 involving a series of radial pleats 39 and circular sectors overlying the shot and preferably joined or at least tightly abutted or otherwise sealed at the center 40, infolding ends accurately at step 38.

While this invention has utility especially with forming a shotgun cartridge case from light metal such as aluminum and/or its alloys, it is to be understood that other suitable materials may be employed with or without annealing and that various other changes and modifications can be made without departing from the spirit and scope of this invention as set forth in the appended claims.

What is claimed is:

1. A method of producing from a metal blank a shell case having a relatively thin elongated tubular sidewall and an open mouth portion thinner than said sidewall, said method comprising (a) placing a slug of material in a die having a restricted opening,

(b) positioning a punch concentrically in said restricted opening to define an annular space between said punch and die corresponding to the desired sidewall thickness of said case,

(c) extruding said slug in one direction through said annular space and around said punch to form a tubular case,

(d) enlarging the diameter of the leading end of said case by expanding it outwardly around an enlargement formed on the other end of said punch and,

(e) driving said case in the opposite direction with said punch through said restricted die opening to draw and thin the enlarged leading end of said casing to a final diameter equal to the diameter of said case.

2. The method of producing from a blank a tubular shell case having a relatively thin elongated sidewall portion intermediate a base and an open thinner-walled mouth extension, said case being of substantially uniform external diameter along at least said sidewall portion and mouth extension, said method comprising (a) pressing a blank in a single pass in an extrusion die to forwardly elongate part of said blank through an annular die orifice of desired diameter back over the end of a punch and along said punch for a predetermined length to form a sidewall portion and an end extension,

(b) simultaneously bulging said extension as it is formed to a diameter in excess of the sidewall diameter, and

(c) driving said bulged end extension reversely with said punch through said die to draw said bulged extension to the external diameter of said sidewall and to a final length of uniformly reduced wall thickness relative to said sidewall.

3. An apparatus for fabricating from a blank a tubular shell case having a base, a relatively thin sidewall portion integral with said base and elongated therefrom and an open thinner-walled mouth extension of substantially the same uniform external diameter as said sidewall portion, the combination comprising a die for receiving a blank, said die having a restricted opening at one end thereof, a punch having one enlarged end receivable in said restricted opening in spaced relationship thereto to define an annular orifice between said punch and die, said punch having a second enlarged portion spaced from said one enlarged end by a distance approximately equal to the length of desired sidewall and having an outside diameter greater than the diameter of said one enlarged end but less than the diameter of said opening, a ram receivable in an opposite direction in the other end of said die to press against said blank for extruding part of said blank through said orifice back over said punch to form a tubular sidewall and a mouth extension bulged outwardly over said second enlarged portion, means for retracting said ram while driving said punch to carry said bulged mouth extension reversely through said restricted die opening to draw said extension to a length of uniformly reduced wall thickness relative to the thickness of said sidewall.

References Cited UNITED STATES PATENTS 2,237,993 4/1941 Kerbuly 2933 2,840,884 7/1958 Biginelli 291.3 2,842,057 7/1958 Dunn 102-42 2,904,873 5/1959 Hild 29--1.3 2,897,758 8/1959 Miller et a1 102-42 RICHARD H. EANES, JR., Primary Examiner.

BENJAMIN A BORCHELT, Examiner.

R. F. STAHL, Assistant Examiner. 

1. A METHOD OF PRODUCING FROM A METAL BLANK A SHELL CASE HAVING A RELATIVELY THIN ELONGATED TUBULAR SIDEWALL AND AN OPEN MOUTH PORTION THINNER THAN SAID SIDEWALL, SAID METHOD COMPRISING (A) PLACING A SLUT OF MATERIAL IN A DIE HAVING A RESTRICTED OPENING, (B) POSITIONING A PUNCH CONCENTRICALLY IN SAID RESTRICTED OPENING TO DEFINE AN ANNULAR SPACE BETWEEN SAID PUNCH AND DIE CORRESPONDING TO THE DESIRED SIDEWALL THICKNESS OF SAID CASE, (C) EXTRUDING SAID SLUG IN ONE DIRECTION THROUGH SAID ANNULAR SPACE AND AROUND SAID PUNCH TO FORM TUBULAR CASE, 